Nanofiber Fabry-Perot microresonator for non-linear optics and cavity quantum electrodynamics

We experimentally realize a Fabry-Perot-type optical microresonator near the cesium D2 line wavelength based on a tapered optical fiber, equipped with two fiber Bragg gratings which enclose a sub-wavelength diameter waist. Owing to the very low taper losses, the finesse of the resonator reaches F = 86 while the on-resonance transmission is T = 11 %. The characteristics of our resonator fulfill the requirements of non-linear optics and cavity quantum electrodynamics in the strong coupling regime. In combination with its demonstrated ease of use and its advantageous mode geometry, it thus opens a realm of applications.Comment: 4 pages, 3 figure

Tin-selenium compounds at ambient and high pressures

SnxSey crystalline compounds consisting of Sn and Se atoms of varying composition are systematically investigated at pressures from 0 to 100 GPa using the first-principles evolutionary crystal structure search method based on density functional theory (DFT). All known experimental phases of SnSe and SnSe2 are found without any prior input. A second order polymorphic phase transition from SnSe-Pnma phase to SnSe-Cmcm phase is predicted at 2.5 GPa. Initially being semiconducting, this phase becomes metallic at 7.3 GPa. Upon further increase of pressure up to 36.6 GPa, SnSe-Cmcm phase is transformed to CsCl-type SnSe-Pm3m phase, which remains stable at even higher pressures. A metallic compound with different stoichiometry, Sn3Se4-I43d, is found to be thermodynamically stable from 18 GPa to 70 GPa. Known semiconductor tin diselenide SnSe2-P3m1 phase is found to be thermodynamically stable from ambient pressure up to 18 GPa. Initially being semiconducting, it experiences metalization at pressures above 8 GPa

Efficient channeling of fluorescence photons from single quantum dots into guided modes of optical nanofiber

We experimentally demonstrate the efficient channeling of fluorescence photons from single q-dots on optical nanofiber into the guided modes, by measuring the photon-count rates through the guided and radiation modes simultaneously. We obtain the maximum channeling efficiency to be 22.0 (\pm4.8)% at fiber diameter of 350 nm for the emission wavelength of 780 nm. The results may open new possibilities in quantum information technologies for generating single photons into single-mode optical-fibers.Comment: 5 pages, 4 figure

SARS CoV subunit vaccine: Antibodymediated neutralisation and enhancement

1. A SARS vaccine was produced based on recombinant native full-length Spike-protein trimers (triSpike) and efficient establishment of a vaccination procedure in rodents. 2. Antibody-mediated enhancement of SARS-CoV infection with anti-SARS-CoV Spike immune-serum was observed in vitro. 3. Antibody-mediated infection of SARS-CoV triggers entry into human haematopoietic cells via an FcγR-dependent and ACE2-, pH-, cysteine-protease-independent pathways. 4. The antibody-mediated enhancement phenomenon is not a mandatory component of the humoral immune response elicited by SARS vaccines, as pure neutralising antibody only could be obtained. 5. Occurrence of immune-mediated enhancement of SARS-CoV infection raises safety concerns regarding the use of SARS-CoV vaccine in humans and enables new ways to investigate SARS pathogenesis (tropism and immune response deregulation)

Atom trapping and guiding with a subwavelength-diameter optical fiber

We suggest using an evanescent wave around a thin fiber to trap atoms. We show that the gradient force of a red-detuned evanescent-wave field in the fundamental mode of a silica fiber can balance the centrifugal force when the fiber diameter is about two times smaller than the wavelength of the light and the component of the angular momentum of the atoms along the fiber axis is in an appropriate range. As an example, the system should be realizable for Cesium atoms at a temperature of less than 0.29 mK using a silica fiber with a radius of 0.2 $\mu$m and a 1.3-$\mu$m-wavelength light with a power of about 27 mW.Comment: 5 pages, 5 figure

Multiorder coherent Raman scattering of a quantum probe field

We study the multiorder coherent Raman scattering of a quantum probe field in a far-off-resonance medium with a prepared coherence. Under the conditions of negligible dispersion and limited bandwidth, we derive a Bessel-function solution for the sideband field operators. We analytically and numerically calculate various quantum statistical characteristics of the sideband fields. We show that the multiorder coherent Raman process can replicate the statistical properties of a single-mode quantum probe field into a broad comb of generated Raman sidebands. We also study the mixing and modulation of photon statistical properties in the case of two-mode input. We show that the prepared Raman coherence and the medium length can be used as control parameters to switch a sideband field from one type of photon statistics to another type, or from a non-squeezed state to a squeezed state and vice versa.Comment: 12 pages, 7 figures, to be published in Phys. Rev.

Large negative and positive delay of optical pulses in coherently prepared dense Rb vapor with buffer gas

We experimentally study the group time delay for a light pulse propagating through hot Rb vapor in the presence of a strong coupling field in a $\Lambda$ configuration. We demonstrate that the ultra-slow pulse propagation is transformed into superluminal propagation as the one-photon detuning of the light increases due to the change in the transmission resonance lineshape. Negative group velocity as low as -c/10^6=-80 m/s is recorded. We also find that the advance time in the regime of the superluminal propagation grows linearly with increasing laser field power.Comment: 5 pages, 6 figure

Testing Western Media Icons Influence on Arab Women’s Body Size and Shape Ideals: An Experimental Approach

Western media globalization is implicated in the spread of the thin body ideal to traditional societies. Qatar—a small conservative Middle-Eastern country—has recently witnessed rapid Westernization, but the influence of Western media icons on women’s body image dissatisfaction has rarely been studied here. A 2 (celebrity or model) × 3 (thin, average, or heavy) plus a control condition between-subject experiment tested the primary hypothesis that exposure to images of thin Western models or celebrities promotes a thinner body ideal compared to neutral images. A sample of young women (n = 1145) was randomly assigned to experimental images as part of an online survey. After exposure to images, participants rated their current and desired body size and shape, reported celebrity liking, and evaluated their favorite celebrity’s body. We found little support for the desire of thinness. Viewing thin- and average-sized celebrities was significantly associated with desiring a heavier and a thinner look (respectively) among those favoring thin celebrities. Images of thin models induced the desire for a curvaceous body figure with hips especially among those favoring celebrities with hips. The findings highlight important nuances in the influence of Western media icons on body image among women in a non-Western culture